The invention relates to a television pick-up tube, comprising an electron source for emitting an electron beam to an image pick-up face, a horizontal deflection device for deflecting the electron beam across the image pick-up face along an image line, a vertical deflection device for deflecting the electron beam in a direction transversely of the image line, and a magnetic deflection element for periodic deflection of the electron beam between transverse positions situated to both sides of the image line during deflection of the electron beam along the image line.
The invention also relates to a deflection system for use in such a television pick-up tube.
A television pick-up tube of this kind is known from U.S. Pat. No. 4,710,799.
The cited Patent Specification describes a television pick-up and reproduction system in which the television pick-up tube and the television monitor are provided with a further magnetic or electrostatic deflection element whereby the electron beams can be deflected so that they traverse an undulating path around the image lines across the image pick-up face of the television pick-up tube and the image display face of the television monitor. The vertical resolution is thus enhanced.
When use is made of a television pick-up tube whose image pick-up face is large in comparison with the beam diameter, for example as in medical imaging systems, the image pick-up face being scanned in a comparatively small number of image lines (625 instead of 1250) in the case of low-resolution imaging, charge is liable to remain between the image lines, which charge is not compensated for by the electron beam. A positive charge accumulation attracts the electron beam in an undesirable manner so that an annoying local flicker effect occurs in the television image. This effect can be counteracted by deflecting the electron beam along a path undulating around the image lines.